Fabrication And Study Of Optical And Electric Properties Of Al(In)n Semiconducting Film

AlInN is III-nitrides ternary alloy. Its properties could be modulated by changing the composition. Therefore, AlInN possesses huge modulation ranges of physical properties, excellent performance. Also, its lattice is matched to core materials like GaN, which is more superior to AlGaN or InGaN. However, the preparation of high quality AlInN is rather difficult. III-nitrides superlattice is another hot investigation, and the current research is focused on AlN/GaN and AlGaN/GaN. Contrarily AlN/InN has been paid little attention. Due to the huge discrepancies of bandgap and electric properties between AlN and InN, AlN/InN superlattice structures possibly have great potential application prospect.This thesis deals with the research on quality improvement of AlInN film and AlN/InN and AlN/GaN superlattices band structures. The main results are given as below:1. In-rich AlInN films (AlN content 0.24-0.31) with improved quality have been grown onto various buffers by radio-frequency reactive sputtering deposition. The films were measured by X-ray diffraction, cross-sectional transmission electron microscopy and other methods. Furthermore, the growth mechanism was discussed based on these measurements. Our study reveals that the (0002) preferred orientation increases with the decrease of Ar/N2 ratio and ambience pressure at low growth temperature (~300℃), while the higher pressure and N2 percentage are in favor of grain growth, and thermal annealing at high temperature (~500℃) can improve the (0002) orientation but direct deposited AlInN at the same temperature will lead to strong quality deterioration. It also indicates that buffer layers have significant influence on AlInN, especially, AlInN/AlN/AlInN film exhibits the best (0002) orientation in comparison to other structures and no a-axis related orientations can be found. Moreover, AlInN and TiN could be the preferable buffer materials than AlN for AlInN growth, while SiNx is not the case. By using the TEM measurement,it is found that AlInN probably would form spontaneous Al-rich and In-rich double-buffer structure in initial growth stage. The relation between composition and strain suggests that compressive strain inhibit the incorporation of InN. The electric properties were found to get better with the improvement of films quality.2. The band structures of wurtzite-AlN/InN and AlN/GaN superlattices were calculated by means of Kr?nig-Penney model and deformation potential theory under considering the lattice strain. Our calculations include the variation of band structures with the parameters for the sublayers, and the energy dispersion relations. It was found that by varying the sublayers thickness, the band structures could be well designed in different ways. The strain will change the bandgaps, decrease the band offsets and sub-bands obviously, and make the valence band more complex. In comparison to the experiment results, our model is rather suitable for simulating the narrow-quantum-well structures, while for the wide-quantum-well structures, the build-in field should be considered. Finally, the properties and advantages of superlattices simulating ternary alloys were preliminary studied.